Prosecutors of the federal case against a former National Security Agency contractor have hit a roadblock in the case, Politico reported.

Harold Martin was arrested in 2016 after authorities said they found more than 50 terabytes of electronic information in Martin's home, as well as a massive amount of paper documents, some of which had been classified up to the "Top Secret" level.

He had allegedly removed the information during working for two decades for a number of intelligence agencies, the report said.

U.S. District Court Judge Marvin Garbis suggested in a Feb. 16 order that the volume of information could be problematic for prosecutors, because their case is based on 20 felony charges about Martin illegally keeping individual classified documents without permission.

The judge asked the prosecution and the defense to explain whether the government must be required to prove that he knew he had specific classified documents in his possession, or if he could be convicted of the Espionage Act violations in the claim without proof that he knew, the report said.

Experts said prosecutors might have trouble showing that Martin knew he had specific documents in his stash.

"It's a fascinating, and, for the prosecution, a rather alarming order from the court. It is partly a reflection of the notoriously confusing language of the Espionage Act," Steven Aftergood, a Federation of American Scientists classified information expert, told Politico.

"There has not been a lot of really sophisticated litigation about the awkwardness of treating piles of information as being subject to the Espionage Act because of one piece of that pile. It's a rare situation where the defendant has a plausible argument that he grabbed the wrong pile of documents," Stephen Vladeck, law professor at the University of Texas told Politico.

Prosecutors on Friday said that they did not need to prove Martin knew he had specific documents.

"Such a requirement would cause the absurd result that a defendant could avoid culpability merely by committing a crime of such magnitude that he could claim ignorance of the details… the Defendant's theft and retention of vast quantities of classified documents does not relieve him of culpability for retaining each individual document," the prosecutors wrote, Politico reported.

Defense attorneys have said that Martin began hoarding documents due to mental health issues, in an obsessive attempt to prove that he was capable at his job, the report said.

Each count of retaining national defense information has a potential 10-year prison sentence, the report said.

Martin was expected to plead guilty in January to one charge of retaining information, but no agreement was reached, Politico reported. Prosecutors said that Martin would get no guarantee that the government would drop the other 19 charges, The New York Times reported in January.